Currently available radiologic imaging techniques make it possible to display a localized focus of disease deep within specific organs or tissues of the body. A typical example is the visualization of a small cancerous mass in the breast of a woman. In order to accurately diagnose and effectively treat the disease, it may be necessary for a surgeon to excise a portion of the diseased tissue for microscopic examination and analysis; or for a physician to accurately insert a needle into the mass to aspirate a sample of the abnormal cells or tissue fluid. A recurrent problem for the surgeon or physician is that even with the help of x-ray films, the search for a small lesion or mass often proves extremely difficult; can cause considerable damage to the normal tissues surrounding the lesion; and often fails in the attempt.
In recent years, increasingly sophisticated radiologic imaging methods with greatly improved resolution and tissue contrast have made it possible to identify small or deep-seated lesions in many anatomic sites. Frequently, however, the benign or malignant nature of the lesion remains uncertain. The diagnosis, clinical significance, and treatment may depend upon microscopic examination of tissue or cell samples obtained from the lesion by surgical biopsy if a large sample is required, or by needle biopsy if a small sample would suffice.
Originally, surgical exploration and biopsy were undertaken purely on the basis of the anatomic descriptions of the radiologic images, i.e., the organ or tissue involved and the described position of the lesion within the organ or tissue. Such surgical procedures were sometimes extremely difficult and prolonged because of the great mobility of soft tissues, limitations of surgical access, and imprecision of the descriptions. As a result, a variety of radiologic localization methods have evolved to facilitate and improve the accuracy of surgical and needle biopsy procedures:
a. Skin Markers: Initially, small radiopaque skin markers were placed directly over the target site under radiologic guidance. Indelible ink marks were then transferred onto the skin to guide the surgeon. This approach has proved satisfactory only for superficial lesions but is inadequate for deeper targets, particularly if these are affected by respiratory motion or posture.
b. Simple Needle Markers: Standard hypodermic needles or longer "spinal" needles have been used in the breast and other soft tissues, guided to the target site under radiologic imaging control. They are left in place for the surgeon. However, these marker needles are not well secured in the tissues and may move from their initial location during patient transfer to the operating room or when the patient position is changed.
c. Tissue-Staining Dyes: After placing a simple needle at the target site under radiologic control, various tissue-staining vital dyes have been injected into the soft tissues at the target site and sometimes also along the needle track. The intention is to direct the surgeon along the stained tract to the target tissue. However, the dyes frequently diffuse widely and have poor localizing value except in the hands of highly skilled operators.
d. Hookwires:
(i) The initial localizing wire hook for breast localization was described by Frank in 1979. The Frank localizer comprised a simple insertion needle containing a long thin wire with a hook end which projected through the needle point. The needle and wire are advanced into the tissues together; and the needle is withdrawn when close to the target lesion, leaving the flexible hookwire in place. The main disadvantage is the "one-way street" character of the method. The wire is designed only to be advanced; its position cannot be readjusted once it has been inserted. Furthermore, the wire is very flexible and can be inadvertently pulled out in a series of jerky step-like movements without great difficulty and may damage the tissues. In addition, the wire can be accidentally transected by the surgeon; and it can also incidentally work its way deeper into the breast tissues. PA1 (ii) An improved hookwire was described by Kopans in 1981 with the hook portion initially housed within the needle lumen. With the Kopans device, the wire is released into the tissue only after the needle position is considered satisfactory. A thickened section of the wire was also provided proximal to the hook to reduce the chances of accidental transection. However, this hook is not readjustable once released; is not easily removable; can be accidentally severed; and unintentionally may advance deeper into the tissues. It can also be withdrawn accidentally in stepwise fashion. PA1 (i) A wire with a springy curved hook at its tip that can be withdrawn into its introducer needle is available and known as the Homer localizer. The Homer device allows repeated readjustment of the hook position so that accurate placement of the wire is possible. However, this also reduces the security of the wire which can be inadvertently withdrawn and displaced. The introducer needle can be removed or left in place depending on the radiologist's or surgeon's preference. There is a scythe-like action of the wire as it tries to regain its curved shape in the tissues and damage could occur. PA1 (ii) An introducer needle with a side hole through which an anchored wire barb may protrude is now commercially available as the Hawkins localizer. Its structure is described within U.S. Pat. No. 4,799,495. The anchored hook of the device is retractable by advancing the internalized wire a short distance within the needle lumen, allowing the needle to be repositioned. This anchored hooked-needle design has considerable resistance to accidental withdrawal when the hook is extended. A slidable screw-stop is typically provided on the needle shaft to prevent deeper penetration of the needle and hook. In one variation, the hook can be advanced beyond the needle tip and the introducer needle removed. This leaves only a flexible wire in the tissues with the hook welded at its tip; a variation which is less secure. Other disadvantages include the rigidity of the needle; the risk of the hook advancing deeper unintentionally; and the possibility of breaking the junction between the wire and the hook. PA1 (iii) A biopsy localization needle device with a single retractable side hookwire is described within U.S. Pat. No. 4,790,329. This device allows for on-demand repositioning; and permits the internal hookwire to be completely removed from the tissues and the localization device at will. Once in position, the hookwire extends into the tissues and avoids accidental withdrawal; the device, however, does not prevent an unintended, accidental advance deeper into the tissues.
e. Retractable Hookwires:
Clearly, there remains a recognized and continuing need for an improved biopsy guide device which is held securely in the target tissue; is easily adjustable; is removable without destruction of localized tissue; eliminates the need for additional guide devices; and provides a reliable guidepost for the surgeon or physician to follow. The availability of such an improved biopsy guide would be recognized and acknowledged by physicians and surgeons alike as being a valuable advance in this art.